Heavy oil and bitumen resources are supplementing the decline in the production of conventional light and medium crude oils, and production from these resources is steadily increasing. Pipelines cannot handle these crude oils unless diluents are added to decrease their viscosity and specific gravity to pipeline specifications. Alternatively, desirable properties are achieved by primary upgrading. However, diluted crudes or upgraded synthetic crudes are significantly different from conventional crude oils. As a result, bitumen blends or synthetic crudes are not easily processed in conventional fluid catalytic cracking refineries. Therefore, in either case further processing must be done in refineries configured to handle either diluted or upgraded feedstocks.
Many heavy hydrocarbon feedstocks are also characterized as comprising significant amounts of BS&W (bottom sediment and water). Such feedstocks are not suitable for transportation by pipeline, or refining due to their corrosive properties and the presence of sand and water. Typically, feedstocks characterized as having less than 0.5 wt % BS&W are transportable by pipeline, and those comprising greater amounts of BS&W require some degree of processing or treatment to reduce the BS&W content prior to transport. Such processing may include storage to let the water and particulates settle, and heat treatment to drive off water and other components. However, these manipulations add to operating cost. There is therefore a need within the art for an efficient method of upgrading feedstock having a significant BS&W content prior to transport or further processing of the feedstock.
Heavy oils and bitumens can be upgraded using a range of processes including thermal (e.g. U.S. Pat. No. 4,490,234; U.S. Pat. No. 4,294,686; U.S. Pat. No. 4,161,442), hydrocracking (U.S. Pat. No. 4,252,634), visbreaking (U.S. Pat. No. 4,427,539; U.S. Pat. No. 4,569,753; U.S. Pat. No. 5,413,702), or catalytic cracking (U.S. Pat. No. 5,723,040; U.S. Pat. No. 5,662,868; U.S. Pat. No. 5,296,131; U.S. Pat. No. 4,985,136; U.S. Pat. No. 4,772,378; U.S. Pat. No. 4,668,378, U.S. Pat. No. 4,578,183) procedures. Several of these processes, such as visbreaking or catalytic cracking, utilize either inert or catalytic particulate contact materials within upflow or downflow reactors. Catalytic contact materials are for the most part zeolite based (see for example U.S. Pat. No. 5,723,040; U.S. Pat. No. 5,662,868; U.S. Pat. No. 5,296,131; U.S. Pat. No. 4,985,136; U.S. Pat. No. 4,772,378; U.S. Pat. No. 4,668,378, U.S. Pat. No. 4,578,183; U.S. Pat. No. 4,435,272; U.S. Pat. No. 4,263,128), while visbreaking typically utilizes inert contact material (e.g. U.S. Pat. No. 4,427,539; U.S. Pat. No. 4,569,753), carbonaceous solids (e.g. U.S. Pat. No. 5,413,702), or inert kaolin solids (e.g. U.S. Pat. No. 4,569,753).
The use of fluid catalytic cracking (FCC), or other units for the direct processing of bitumen feedstocks is known in the art. However, many compounds present within the crude feedstocks interfere with these processes by depositing on the contact material itself. These feedstock contaminants include metals such as vanadium and nickel, coke precursors such as (Conradson) carbon residues, and asphaltenes. Unless removed by combustion in a regenerator, deposits of these materials can result in poisoning and the need for premature replacement of the contact material. This is especially true for contact material employed with FCC processes, as efficient cracking and proper temperature control of the process requires contact materials comprising little or no combustible deposit materials or metals that interfere with the catalytic process.
To reduce contamination of the catalytic material within catalytic cracking units, pretreatment of the feedstock via visbreaking (U.S. Pat. No. 5,413,702; U.S. Pat. No. 4,569,753; U.S. Pat. No. 4,427,539), thermal (U.S. Pat. No. 4,252,634; U.S. Pat. No. 4,161,442) or other processes, typically using FCC-like reactors, operating at temperatures below that required for cracking the feedstock (e.g. U.S. Pat. No. 4,980,045; U.S. Pat. No. 4,818,373 and U.S. Pat. No. 4,263,128) have been suggested. These systems operate in series with FCC units and function as pre-treaters for FCC. These pretreatment processes are designed to remove contaminant materials from the feedstock, and operate under conditions that mitigate any cracking. These processes ensure that any upgrading and controlled cracking of the feedstock takes place within the FCC reactor under optimal conditions.
Bitumen feedstocks comprise solids such as, sand and other particulates. Direct processing of bitumen feedstocks must be carried out by contact of a hydrogen-containing gas with the hydrocarbon feed stream at elevated temperatures and pressures. Thus, the major costs of such processing are essentially in obtaining and maintaining of the processing equipment. Examples of the major costs are: vessels and associated furnaces, heat exchangers, distributor plate assemblies, pumps, piping and valves capable of such service and the replacement cost of catalyst contaminated in such service, and the cost of assembling the equipment. Commercial hydroprocessing of relatively low cost feed stocks such as reduced crude oils containing pollutant compounds, requires a flow rate on the order of a few thousand up to one hundred thousand barrels per day, with concurrent flow of hydrogen at up to 10,000 standard cubic feet per barrel of the liquid feed. Vessels capable of containing such a reaction process are accordingly cost-intensive both due to the need to contain and withstand corrosion and metal embrittlement by the hydrogen compounds, sulfur compounds and the solids within the bitumen feedstocks, while carrying out the desired reactions at elevated pressure and temperatures. Pumps, piping and valves for handling fluid streams containing hydrogen at such pressures and temperatures are also costly, because at such pressures seals must remain hydrogen impervious over extended service periods of many months. Fine and ultra-fine, clays, sands and particulates in the heavy oil and bitumen may reduce the effectiveness of the seals overtime, as well. It is also cost-intensive to insure that all of the equipment are assembled, manufactured and/or maintained correctly.
Even taking all the precautions taken during the upgrading process and with the assembly, manufacture and maintenance of the equipment to ensure the purest end product, one skilled in the art understand it is inevitable that the end product often comprises fine and ultra-fine clays, sands and particulates that are from the bitumen or petroleum feedstock.